Conventional cleaning apparatus and processes typically utilise an aqueous method or a method which utilises chemicals. Consider, for example, household washing machines or dry cleaning, which is more commonly used within industrial cleaning processes.
Domestic cleaning of clothes or other fabric articles typically involves hand washing processes or more commonly front or top-loaded drum-style washing machines which employ both an aqueous and mechanical cleaning process, often requiring large amounts of detergents and stain removal chemicals. Such machines have a high consumption of both water and power, with an average domestic washing machine using between 9-10 liters of water and consuming approximately 0.75 KW-hour electricity per wash load. Once the items are cleaned, the very nature of the cleaning process leaves the articles quite wet and requires subsequent drying, either in an inefficient machine such as a commercial tumble drier or through inefficient use of a building's heating system (radiators, etc.) or through outside drying via direct sunlight and/or wind.
Dry cleaning processes typically involve extensive use of hydrocarbon solvents such as perchloroethylene, and the storage, treatment and disposal of such chemicals may pose environmental concerns. Furthermore, dry cleaning equipment is specialized and is often extremely expensive and non-portable.
The cleaning of carpets and upholstery, both in the domestic as well as industrial environment, typically uses hot water or steam processes and, in many cases, these processes again leave the material soaked to dry out gradually over time. For industrial applications, for example in the transport sector where seats of passenger aircraft, trains and buses require regular cleaning, this can involve periods of “down time” where the vehicle is not used so as to allow the cleaned upholstery to dry.
In modern society, many articles being cleaned using conventional method and apparatus are very lightly or locally soiled. For example, a shirt may have a dirty collar and cuffs and perhaps have an odour in certain regions of the shirt. Nevertheless, the item is fully washed simply because there is a small oil or food stain in a very localised area. In a household setting, the use of a washing machine to clean such items on a daily basis can be excessive, and can result in degradation of the lifetime of the article due to the mechanical nature of the cleaning process and the need, very often, for drying of the garment in direct sunlight.